As used herein, “true colors” or “device-independent colors” denote colors that are visible to the eyes without the need of a device, such as computer equipment, televisions, diodes, light emitting diodes (LEDs), projectors, computer displays, screens or the like. True colors of a surface include those that are visible when light reflects off that surface, or those that can be produced by pigmented compositions coated on the surface, such as paints and coatings. On the other hand, “device-dependent colors” are colors produced by the devices listed above. Typically, the device-dependent colors are produced within the devices by combinations of the spectral ranges within the visible radiation spectrum of electromagnetic radiation. The wavelengths of visible radiation spectrum range from about 380 nm (violet) to about 740 nm (red). In one example, the device-dependent colors can be created by combining different amount of the three primary colors: red (625 nm-740 nm), green (520 nm-565 nm) and blue (435 nm-500 nm) or RGB, e.g., RGB computer monitors. The RGB convention represents approximate emission bands of wavelengths. Device-dependent colors can also be produced by mixtures of four process/primary colors: cyan, magenta, yellow and black or CMYK, e.g., offset printing of color documents. The CMYK convention represents approximate absorption bands of wavelengths. Device-dependent colors based on RGB convention can be converted by known color management systems to CMYK convention and vice versa.
Recently, device-dependent colors based on at least five, seven, nine and up to eleven color primaries, preferably light emitting diodes (LEDs) are disclosed in U.S. Pat. Nos. 7,474,314 and 7,750,917 entitled “Method for Representing True Colors with Device-Dependent Colors on Surfaces And For Producing Paints and Coatings Matching The True Colors” to Carl Minchew and Patrick Chong. Minchew and Chong teach that higher number of color primaries expands the color gamut of the device-dependent colors. The Minchew and Chong device can produce a substantially larger color gamut than the RGB computer/television monitors and CMYK printers.
International published patent application number WO2009/082737 entitled “System for Representing Colors Including an Integrating Light Capsule” to Patrick Chong, Michael Gutman, Carl Minchew and Hugh Fairman further expands the number of color primaries to sixteen and up to thirty-two color primaries, preferably LED primaries, to improve color gamut and to reduce metamerism. These primary colors are mixed in an integrated light capsule to produce a device dependent color that closely matches the true color or device-independent color. Chong, Gutman, Minchew and Fairman show that the number of primaries is inversely proportional to the degree of metamerism, i.e., increasing the number of primaries reduces metamerism. Metamerism is the appearance of two or more colors to be substantially the same under one ambient lighting condition, but may appear to be different colors under another ambient lighting condition. This reference demonstrates that a spectral curve of a device-dependent color made from thirty-two primaries matches a spectral curve of a true color much closer than that of a device-dependent color made from only six primaries. In other words, the effects of metamerism are reduced by increasing the number of primaries.
U.S. Pat. Nos. 7,474,314 and 7,750,917, and international published patent application number WO2009/082737 are incorporated by reference herein in their entireties. While these references represent substantial improvements over RGB and CMYK devices in increased color gamut and low-metameric device dependent colors, there remains a need for improved color matching for device-dependent colors.